Case 1 : My eldest daughter got a quote for new blinds in their new home - the rep was none other than one of her high school friend's Dad. I happened to be at her house when he came and it was a while before they worked it out, but then spent ages chatting about 'said' friend.
Case 2 : My middle daughter went to work for a company that is a production house for my work. While there she met a girl who subsequently became our rep. 'Said' rep in now a FB friend of mine. Recently I was on FB and writing a comment on a friend of my eldest daughter's page, I saw a name in her friends list. Thought it might be the wife of a boy whose family I knew quite well and my kids grew up with so nosy me checked it out and it was. But imagine my surprise when on her 'family' list was the name of the 'said' rep from the production company who is her sister.
Case 3 : A friend of my youngest daughter joined the footy tipping comp I run, so I have got to know her quite well. My Mum, who was adopted, has made contact with her 'birth' mother's and father's families and is friends with quite a few of them on FB. Turns out my youngest daughter's friend went to school with my Mum's nephews wife which none of us would have know if not for it coming up on FB.